Crystal electrode



Nov. 8, 1949 A. E. MILLER 2,487,165

CRYSTAL ELECTRODE Filed Oct. 10, 1946 INVENTOR Aueus'r E, MILLERATTORNEYS Patented Nov. 8, 1949 UNITED STATES PATENT OFFICE CRYSTALELECTRODE August 15. Miller, Cllf'fside Park, N. J.

Application October 10, 1946, Serial No. 702,411

The invention relates to an electrode to be used with a piezoelectriccrystal device as used particularly with high frequency oscillatingcircuits. Two electrodes are used with each crystal one being placedupon each side thereof. The crystal and the two electrodes arecustomarily held in a case or housing of any suitable sort for assemblyor mounting into an electric circuit.

There are several factors which enter into the stability with which thecrystal oscillates in the circuit at the desired frequency. Two of thesefactors are the dimensions of the surface of the conductor carried bythe electrode as well as its spacing from the crystal. The spacing ofthe surface of the conductor from the crystal at very high frequenciesis of the order of microns. Di mensions of this order heretofore havebeen obtained by separately vaporizing thin layers of metal upon thefaces of an insulator or by electronic deposition. These metallic layersfrequently peel off, are extremely difficult to control as to theirthickness in order to obtain proper spacing between the conductorsurface and the crystal, the conducting surfaces or layers on oppositefaces are difilcult to connect electrically, and exhibit otherdisadvantages.

It is an object of the invention to construct a crystal electrode inwhich the conducting material has integrallflanges by which it is lockedto an insulator body.

Another object of the invention is to construct a crystal electrode inwhich the dimensions of the surface of the metal may be selected asdesired.

Another object of the invention is to construct a crystal electrode inwhich either face of the electrode may be utilized as the conductingface which is mounted adjacent tothe crystal depending upon thedimension of the conducting surface which may be desired.

A further object is to construct an electrode which is more easilymanufactured.

A still further object is to provide a new and novel method of making acrystal electrode.

Other objects of the invention are more apparent from the followingdescription when taken with the accompanying drawings illustratingdifferent embodiments thereof in which:

Figure 1 is a cross section through an enlarged crystal electrode.

Figure 2 is a plan view of the electrode of Figure 1.

Figure 3 is a cross section through an enlarged crystal electrode ofanother form.

16 Claims. (Cl. 171-327) Figure 4 is a plan view of the crystal ofFigure 3.

The crystal electrode includes an insulating body I0 of any suitableinsulating material, a ceramic being preferred because this materialstands up under relatively high temperatures. The body has two oppositeflat faces one of which carries a recess Ii. Preferably some portion ofor all of the side edge or edges i2 of the recess are inclinedoutwardly. Since the electrode particularly shown is circular, theentire circumference of the edge is shown inclined. It is clear,however, that the entire edge need not be inclined and with arectangular or square form of metallic or conducting surface, forexample, one or more of the edges may be inclined outwardly. Theopposite face of the insulating body 10 preferably carries a recess 13and the edge or edges i4 thereof also may be inclined outwardly if it isdesired to utilize this face as a conducting or metallic surface to bepositioned adjacent to a crystal as will appear more fully hereinafter.The recesses shown are fiat-bottomed and are relatively thin in order toconserve metal. An opening or hole 15 extends through the body H] whichhole has a dimension less than that of the recesses and connects therecess in one face of the body with the opposite face of the body orwith the opposite recess if one is provided.

The recesses and hole are filled with an electrically conductivematerial in plastic form. The conducting material may be any metal suchas silver, copper, aluminum and the like or any alloy, amalgam orcomposition which is electrically conducting. The metal is in powderedor comminuted form and is mixed with about 10% of powdered. borosilicateglass or other suitable binder which will harden or can be hardenedafter it is applied. Preferably the binder is heat fusible, such aspowdered borosilicate glass, at a temperature lower than that at whichthe body becomes plastic or is destroyed. A liquid binder is also mixedinto the dry composition or mixture so that the mass has a pastyconsistency and adheres together. Such compositions or mixtures areknown. The electrode body with the paste conductor material filling therecesses and the hole, is heated such as in an oven to drive off theliquid binder and to fuse the borosilicate glass thereby bindingtogether the metallic powder and attaching the fused material to thebody. A hardened metallic conductor results from the powdered metallicmaterial held together by the binder which conductor has flanges l6 and[l on acsmoc each side of the body connected by a center plug ll to forman integral whole. The conducting material or metal is therefore lockedor flrmly anchored to the body by the flanges.

One of the faces of the electrode is then dished such as cylindricallyconcave or spherically concave. Grinding of the face or faces of theelectrode may be utilized for this purpose so that points at the edge ofthe body are above or higher than the face of the metallic conductor.The grinding may be controlled so that the highest point of the surfaceof the conductor is one or more microns below the higher points at theedge of the electrode or the body. Optical grinding permits theconcavity to be acurately controlled and thereby enables the spacing ofthe conducting surface below the high points at the outer edge ofelectrode to be of the order of microns. With a circular electrode whichhas been spherically ground, the entire peripheral edge of the electrodeor body is higher than the surface of the conductor.

With an electrode in which the recess has an inclined edge or edges i2,the metallic conducting flange fused within the recess also has aninclined edge or edges. This enables the electrode to be ground with anelectrically conducting surface adjacent to the crystal of any desireddimension. In other words the face of the electrode may be initially ati9, andground flat until the outside dimension of the conducting surfaceis slightly larger than the desired dimension. Upon grinding the faceconcave, the dimension is reduced slightly more. The initial grinding ofthe face of the electrode would be to an extent sumciently to give theapproximate desired dimension and the concave grinding reduces thesurface to the desired dimension. A single concave grinding operationmay be used the extent of which is determined by the surface dimensiondesired. It is this dished or concave face that is placed against thecrystal with the higher edges of the body engaging the crystal. Thedegree or radius of concavity with which the face of the electrode isground determines the spacing of the conducting surface from thecrystal.

The recess i3 as previously mentioned may also have its edge or edges i4inclined outwardly. The

outer r maximum dimension of this recess may be approximately theminimum dimension of the recess Ii so that this face-of the electrodemay be ground and placed adjacent to the crystal in the event that asmaller surface area is desired. This face also may be initially groundto 'an approximate dimension and the concave or dished grinding giving asurface for the conductor of any desired dimension. With an electrode soconstructed an increased range of dimensions for the surface adjacent tothe crystal may be achieved. Y

The electrode shown in Figure 3 includes a body 20 of insulatingmaterial having a recess 2! in one face thereof and a recess 22 in theother face thereof. These recesses have inclined edges which merge toform a connecting opening 23. The angle of inclination of the edges maybe the same or different as desired. These recesses are filled with thehardening o-r fusible plastic conducting material and allowed to hardenor is fused. This electrode also may be ground initially upon one faceuntil the surface of the conducting material is approximately of thedesired dimension after which it is ground with a concave or dished face24. The conducting material forms flanges 25 and 26 on opposite faces ofthe elec- I 4 trode or body which are integrally connected with eachother through the Opening 23 and hence lock or anchor the same to thebody. A spring contact 5 or a wire W may be soldered to the oppositeconducting face of each electrode in order to establish electricalconnection therewith.-

Although in the preferred forms recesses are provided in the oppositeface of the body from the face which is concaved and'placed adjacent tothe crystal. the integral flange construction can be secured withoutthis recess in each face merely by filling the recess provided in oneface of the body and the hole through the body with the fusible plasticconducting composition and spreading the composition over the other faceof the electrode. When fused or hardened the hardened conductor ormetallic composition has flanges on opposite sides of the body which areintegrally connected by the plug of material in the hole and therebyanchor the conductor to the body.

So far as -the method of obtaining a metallic electrode surface of thedesired surface area or dimension and desired spacing of the surfacefrom the surrounding edge or edges are concerned, the central metallicconducting material 16 and 25 may be secured to the ceramic body in anyway desired although the fusing method particularly described ispreferred.

This invention is presented to fill a need for improvements in electrodefor piezo crystal. It is understood that various modifications instructure, as well as changes in mode of operation, assembly, and mannerof use, may and often do occur to those skilled in the art, especiallyafter benefiting from the teachings of an invention' Hence, it will beunderstood that this disclosure is illustrative of preferred means ofembodying the invention in useful form by explaining the construction,operation and advantages thereof.

What is claimed is:

1. An electrode for-a piezo electric crystal device comprising a body ofinsulating material having opposite faces; a cavity in the bodyincluding a recess in at least one face thereof of a lesser dimensionthan the outer dimension of the body, and the body having an openingtherethrough of a lesser dimension than the recess to connect the latterwith the other face of the body; an electrical conducting materialfilling the recess and the connecting opening and extending over theopposite face of the body to form an integral whole with connectedflanges which is locked to the body by the flanges, and the recessedface of the electrode being dished to space the surface of theelectrically conducting material below the outer edge of the body.

2. An electrode for a piezo electric crystal device comprising a body ofinsulating material having opposite faces, a cavity in the bodyincluding a recess in at least one face thereof of a lesser dimensionthan the outer dimension of the body, and the body having an openingtherethrough of a lesser dimension than the recess to connect the latterwith the other face of the body, a heat fusible electrical conductingmaterial filling the recess, the connecting opening and extending overat least a portion of the opposite face of the body to form an integralwhole with connected flanges which is locked to the body by the flanges,and the recessed face of the electrode being dished to space the surfaceof the electrically conducting material below the outer edge of thebody.

3. An electrode for a piezo electric crystal device comprising a body ofinsulating material, a cavity in the body including a recess in eachface thereof of a lesser dimension than the outer dimension of the body,and the body having an opening connecting the recesses through the body'at a lesser dimension than the recesses, an electrical conductingmaterial in both recesses and the connecting opening to form an integralwhole with connected flanges which is locked to the body by the flanges,and one of the faces of the electrode being dished to space the surfaceof the electrically conducting material below the outer edge of thebody.

4. An electrode for a piezo electric crystal device comprising a body ofinsulating material; a cavity in the body-including a recess in eachface thereof of a lesser dimension than the outer dimension of the bodyand having a flat bottom, and the body having a hole extending betweenthe recesses and through the body at a lesser dimension than therecesses; an electrical conducting material in both recesses and thehole to form an integral whole with connected flanges a cavity in thebody including a recess in at least one face thereof of a lesserdimension than the outer dimension of the body, the side edge of therecess inclining outwardly, and the body having an opening through thebody at a lesser dimension than the recesses to connect the recess withthe other side of the body; an electricalconducting material filling therecess with the inclined side and the connecting opening and extendingaround the opening on the other side of the body to form an integralwhole with connected flanges which is locked to the body by the flanges,and the face of the electrode having the recess with an inclined sideedge being dished to space the surface of the electrically conductingmaterial below the outer edge of the body and provide a conductorsurface of a desired dimension.

6. An electrode for a piezo electric crystal device comprising a body ofinsulating material; a cavity in the body including a recess in eachface thereof of a lesser dimension than the outer dimension of the body,the side edge of at least one recess being inclined outwardly, and thebody having an opening connecting the recesses through the body andhaving a lesser dimension than the recesses; an electrical conductingmaterial in both recesses and the connecting opening to form an integralwhole with connected flanges which is locked to the body by the flanges,and the face of the electrode having the recess with an inclined edgebeing dished to space the surface of the electrically conductingmaterial below the outer edge of the body and to provide a conductingsurface of a desired dimension.

7. An electrode for a piezo electric crystal device comprising a body ofinsulating material, a cavity in the body including a recess in eachface thereof of a lesser dimension than the outer dimension of the body,each recess having an edge inclined outwardly, and the body having anopening through the body of a lesser dimension than the recesses andconnecting the same; an electrical conducting material filling bothrecesses and the connecting opening to form an integral whole withconnected flanges which is locked to the body by the flanges, and atleast one of the 6 faces of the electrode being dished to space thesurface of the electrically conducting material below the outer edge ofthe body and provide a conducting surface of a desired dimension.

8. An electrode for a piezo electric crystal device comprising a body ofinsulating 'material, a cavity in the body including a recess in eachface thereof of a lesser dimension than the outer dimension of the bodyand having a flat bottom, each recess having an edge incliningoutwardly, the maximum dimension of one recess being approximately thesame as the lesser dimension of the other recess, and the body having ahole through the body of a lesser dimension than the recesses to connectthe same; an electrical conducting material filling both recesses andthe connecting opening to form an integral whole with connected flangeswhich is locked to the body by the flanges, and at least one of thefaces of the electrode being dished to space the surface of theelectrically conducting material below the outer edge of the body.

9. A method of making an electrode for a piezo electric crystal devicehaving a body of insulating material and a cavity in the body includinga recess in at least one face thereof of a lesser dimension than theouter dimension of the body and having an edge inclining outwardly, andan opening through the body of a lesser dimension than the recessmaterial comprising filling the recess and the connecting opening andspreading over the opposite face of the body with an initially plasticelectrical conducting material to form connected flanges, hardening theconducting material to form an integral whole which is locked to thebody by the flanges. and grinding concave the face of the electrodehaving the recess to space the surface of the electricall congugtingmaterial below the outer edge of the 10. A method of making an electrodefor a piezo electric crystal device having a body of insulating materialand a cavity in the body including a recess in at least one face thereofof a lesser dimension than the outer dimension of the body and anopening through the body of a lesser dimension than the recess materialcomprising filling the recess and the connecting opening with andspreading over the opposite face of the body an initially plastic andfusible electrical conducting material to form connected flanges, fusingthe conducting material with heat at a temperature high enough to fusethe conducting material but insufficient to affect the body to form anintegral whole which is locked to the body by the flanges, and grindingconcave the face of the electrode having the recess to space the surfaceof the electrically conducting material below the outer edge of thebody.

11. A method of making an electrode for a piezo electric crystal devicehaving a body of insulating material and a cavity in the body includinga recess in at least one face thereof of a lesser dimension than theouter dimension of the body and having an edge inclining outwardly, andan opening through the bod of a lesser dimension than the recessmaterial comprising filling the recess and the connecting opening andspreading over the opposite face of the body with an initially plasticelectrical conducting mate rial to form connected flanges, hardening theconducting material to form an integra1 whole which is locked to thebody by the flanges, grinding the face of the electrode having therecess with the inclined edge until the conducting material is ofapproximately the desired dimension, and grinding concave this face ofthe electrode to space the surface of the electrically conductingmaterial below the outer edge of the body.

12. A method of making an electrode for a piezo electric crystal devicehaving a body of insulating material and a cavity in the body includinga recess in at least one face thereof of a lesser dimension than theouter dimension of the body and having an edge inclining outwardly, andan opening through the body of a lesser dimension than the recessmaterial comprising filling the recess and the connecting opening andspreading over the opposite face of the body with an initially plasticand heat fusible electrical conducting material to form connectedflanges, fusing the conducting material at a temperature high enough tofuse the conducting material but insufficient to affect the body to forman integral whole which is locked to the body by the flanges, grindingthe face of the electrode having the recess with the inclined edge untilthe conducting material is of approximate y the desired dimension, andgrinding concave this face of the electrode to space the surface of theelectrically conducting material below the outer edge of the body.

13. An electrode for a piezo electric crystal device comprising a bodyof insulating material having opposite faces; the body having an openingtherethrough at least one edge thereof of a lesser dimension than theouter dimension of the body, the opening having an inclined edgeproviding different sectional areas parallel with a face of the body, anelectrical conducting material filling the opening, and the face of theelectrode having the edge of the opening spaced from the outer dimensionof the body being dished to a dimension greater than the face of theconducting material and to a depth with respect to the outer edge of theelectrode corresponding with the desired spacing of the surface of theelectrically conducting material from the crystal.

14. An electrode for a piezo electric crystal device comprising a bodyof insulating material having opposite faces, a cavity extending throughthe body and between the faces, at least one face of the cavity having alesser dimension than the outer dimension of the body, and the cavityhav ing at least one sectional area spaced from the face of the body ofa lesser dimension than another sectional area; an electrical conductingmaterial filling the cavity to form an integral whole which is locked tothe body, and the recessed face of the electrode being dished to spacethe surface of the electrically conducting material below the outer edgeof the body.

15. A piezo crystal combination comprising a piezo crystal having flatfaces, an electrode engaging each face of the crystal at its outeredges; at least one electrode including a body of insulating materia1having opposite faces, the body having an fopening therethrough at leastone diameter greater than the face of the conducting material and to adepth with respect to the outer edge of the body corresponding with thedesired spacing of the surface of the electrically conducting materialfrom the crystal.

16. A piezo crystal combination com rising a piezo crystal having fiatfaces, an electrode engaging each face of the crystal at its outeredges; at least one electrode including a body of insulating materialhaving opposite faces, the body having an opening therethrough at leastone edge thereof of a lesser dimension than the outer dimension of thebody, the opening having an inclined edge providing different sectionalareas parallel with the face of the body, an electrical conductingmaterial filling the opening, and a face of the electrode having theedge of the opening spaced from the outer dimension of the body beingdished to a diameter greater than the face of the conducting materialand to a depth with respect to the outer edge of the body correspondingwith the desired spacing of the surface of the electrically conductingmaterial from the crystal.

AUGUST E. MILLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,783,014 Hansell Nov, 25, 19302,076,060 Bechmann et al. Apr. 6, 1937 2,146,994 Schroter et al. Feb.14, 1939 2,252,277 Tate et a1 Aug. 12, 1941 2,255,184 Osenberg Sept. 9,1941 2,366,274 Suth Jan. 2, 1945

